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Video Scaler v4.0 User Guide
UG805 March 1, 2011
Chapter 4:
Video I/O Interface and Timing
Valid video data is written into the input line buffer using
active_video_in
as a write-
enable. This is shown in
Figure 4-1
for the 8-bit 4:2:2 case The
active_video_in
signal
must remain in a high state for the duration of the active input line.
The scaler is capable of accepting and delivering 4:4:4 (e.g., RGB), 4:2:2, and 4:2:0 chroma
formats.
It will not convert between chroma formats.
For delivery of 4:4:4 video data, a
third channel would be added to this diagram, and the three channels would be either R,
G, and B or Y, Cb, and Cr. It is necessary to clarify the I/O format. For bandwidth, 4:2:0 is
essentially the same as 4:2:2 horizontally, but is half the bandwidth vertically. Different
signaling is required for the delivery of the YC4:2:2: and YC4:2:0 chroma systems. The
luma (Y) input is a full bandwidth 8-bit input on
video_data_in[7:0].
The chroma for
both 4:2:0 and 4:2:2 is also a full-bandwidth input on
video_data_in[(data_width*2)-1:data_width]
, but Cb and Cr are interleaved
on a pixel basis, as shown in
Figure 4-1
for the 8-bit case. An additional input
active_chroma_in
is required in the 4:2:0 case. This must be asserted high on all lines
for 4:2:2, but only for alternate lines for 4:2:0, as shown in
Figure 4-2
.
When running the scaler using Live Mode, you are likely to derive the
active_video_in
from timing signals such as horizontal sync or embedded flags like EAV and SAV. In this
case, you will have calculated that the line-rate at the input, often defined by the input
video format, is sufficiently low that the host system will never need to wait for the
line_request
signal to be asserted.
However, in contrast, you may calculate that this is not possible, and that the scaler must
hold off the input data. The
line_request
flag deasserted state should be used to hold
off the write-operation for a new line. Since it is impossible to hold off a live video feed, the
data must be fed (directly or indirectly) from a frame buffer, and the appropriate external
control provided (Memory Mode).
X-Ref Target - Figure 4-1
Figure 4-1:
Scaler 8-bit 4:2:2 Input Timing
X-Ref Target - Figure 4-2
Figure 4-2:
Scaler 8-bit 4:2:0 Input Chroma Validation
video_in_clk
line_re
qu
e
s
t
a
ctive_video_in
video_d
a
t
a
_in (7:0) (L
u
m
a
)
video_d
a
t
a
_in (15:
8
) (Chrom
a
)
Y
C
b
0
0
Cr
0
C
b
n
Cr
n
C
b
n+2
Cr
n+2
Cr
s
ize-2
Y
1
Y
n
Y
n+1
Y
n+2
Y
n+
3
Y
s
ize-1
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chrom
a
_in
video_d
a
t
a
_in (7:0)_(L
u
m
a
)
video_d
a
t
a
_in (15:
8
)_(Chrom
a
)
Line1
V
a
lid
Line2
N/V
Line
3
V
a
lid
Line4
N/V
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Содержание LogiCORE IP
Страница 1: ...LogiCORE IP Video Scaler v4 0 User Guide UG805 March 1 2011...
Страница 6: ...Video Scaler v4 0 User Guide www xilinx com UG805 March 1 2011...
Страница 14: ...14 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Preface About This Guide...
Страница 18: ...18 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Chapter 1 Introduction...
Страница 20: ...20 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Chapter 2 Overview...
Страница 70: ...70 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Chapter 9 Performance...
Страница 74: ...74 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Appendix A Use Cases...
Страница 92: ...92 www xilinx com Video Scaler v4 0 User Guide UG805 March 1 2011 Appendix B Programmer Guide...
